The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
During processing of substrates such as semiconductor wafers, various processes including deposition, etching and/or other substrate treatments are performed. Substrate processing systems for performing etching typically include a processing chamber with a substrate support such as an electrostatic chuck. A substrate such as a semiconductor wafer may be arranged on the substrate support. A process gas mixture including one or more etching gases and/or carrier gases may be introduced into the processing chamber to etch film on the substrate. Plasma may be struck in the processing chamber to activate chemical reactions.
In some applications, it is desirable to control a bias on the substrate during processing. Spring pins or other connection approaches have been used to apply ground, a DC bias or an AC bias to a backside of the substrate. However, due to mismatch in coefficients of thermal expansion (CTE) between the substrate and components of the ESC, the substrate may move laterally relative to ESC during processing.
Referring now to FIGS. 1-2, examples for providing a connection to a substrate are shown. In FIG. 1, a substrate 14 is arranged on a substrate support 10 such as an ESC. The substrate support 10 includes an upper layer 16 (such as a bond) and a metal housing 20. A connector 22 passes through the metal housing 20 and is connected to a spring pin 24. An upper end of the spring pin 24 is biased against a bottom surface of the substrate 14. The spring pin 24 remains in a fixed lateral position during substrate processing. However, the substrate 14 moves laterally due to CTE thermal mismatch between the substrate and components of the substrate support 10. The lateral movement causes rubbing along the bottom surface of the substrate 14, which wears the spring pin 24 and damages the substrate 14.
In FIG. 2, a contact 30 is soldered to a bottom surface of the substrate 14. A conductor 32 is soldered to the contact 30 and attached to the connector 22. While the conductor 32 allows movement of the contact 30 with the substrate 14 during processing, the conductor 32 and the contact 30 are typically made of different materials and experience CTE mismatch. Over time, a solder joint between the conductor 32 and the contact 30 experiences fatigue due to the CTE mismatch between the conductor 32 and the contact 30 and eventually fails.